Well that was a quick and quite one. Only one person was able to find the item and get it off the boss. And he got it from the hardest boss with one. It was Shisenshi/Falgore who got it from the darken beast lord. The other two mobs that had one was the storm commander in the outpost, and dark bishop in the black fort.
So next time better get a better hustle on. I know it was kinda a surprise, but I was bored and a free 30 min to make it happen.